1. Field of the Invention
The present invention relates to a liquid crystal display and a driving method thereof.
2. Description of Related Art
A liquid crystal display (LCD) includes a pair of panels including a plurality of pixel electrodes and a common electrode and a liquid crystal (LC) layer arranged between the panels and having dielectric anisotropy. The pixel electrodes are arranged in a matrix and connected with switching elements, such as thin film transistors (TFTs). The pixel electrodes are supplied with data voltages through the TFTs in a row by row manner. The common electrode covers an entire surface of a panel and is supplied with a common electrode. The pixel electrode, the common electrode, and the LC layer arranged therebetween form a LC capacitor. The LC capacitor and the switching element are the basic elements forming a pixel.
The LCD generates an electric field in the LC layer by applying voltages to the electrodes, and obtains desired images by controlling the strength of the electric field to vary the transmittance of light incident upon the LC layer.
Among the LCDs, a vertical alignment (VA) mode LCD, which aligns LC molecules such that the long axes of the LC molecules are substantially perpendicular to the panels in the absence of an electric field, is used because such mode has a high contrast ratio and wide reference viewing angle.
The wide viewing angle of the VA mode LCD may be obtained by having cutouts formed in the field-generating electrodes and protrusions formed on the field-generating electrodes. Since the cutouts and the protrusions may determine the tilt directions of the LC molecules, several tilt directions may be used to widen the reference viewing angle.
LCDs are increasingly being used to display motion images. The response time of the liquid crystal is an important characteristic of the LCD. In particular, as the size of the LCD increases, the resolution of the LCD decreases unless the response time of the liquid crystal is increased.
Liquid crystal having a slow response time takes longer for a pixel to reach a desired luminance. The time for obtaining the desired luminance depends on the difference between a target voltage for giving the desired luminance and a previously charged voltage across the LC capacitor of the pixel. Thus, the pixel may not reach the desired luminance by a given time when the voltage difference is large.
To solve the above problem, dynamic capacitance compensation (DCC) for improving the response time without changing the characteristics of the liquid crystal itself may be used. The DCC applies a voltage that is greater than the target voltage to the LC capacitor to reduce the time for reaching the desired luminance. However, the improvement of the response time given by the DCC may be insufficient when the target voltage is greater than the voltage applied by the DCC.
Thus, the LC molecules should be pre-tilted before a voltage that is higher than the target voltage is applied thereto. However, applying such a voltage that is higher requires that the highest target voltage be less than a highest available voltage. As such, the luminance corresponding to the highest target voltage may be relatively low and the number of grays is limited.